Electronic musical instrument



y 1958 P. B. ONCLEY 2,842,021

ELECTRONIC MUSICAL INSTRUMENT Filed May 1'7, 1955 2 Sheets-Sheet 1 OSC TO 'PO WEI? S UFPL Y AMPLIFIER 39 73 I 1 T i .E. 42 E, 7 0

K x A 46 L .J L

VOLTAGE i 3 45 T E INVENTOR. PAUL 5.0NCLEY Aim July s, 1958 Filed May 17, 1955 El IZII 32111 P- B. ONCLEY ELECTRONIC MUSICAL INSTRUMENT 2 Sheets-Sheet 2 INVENTOR. PAUL 5. U/VCAEY tinited States ELECTRONIC MUSICAL INSTRUMENT Paul B. Oncley, Princeton, N. 1., assignor to Gulton Industries, Inc., Metuchen, N. J., a corporation of New Jersey Application May 17, 1955, Serial No. 508,936

4 Claims. (Cl. 841.01)

Because of the large number of oscillators in even a moderate-sized organ, such a system of tone shaping is only economical and practical if the circuitry and design of the tone shaping elements are simple and economical.

- It is, accordingly, a principal object of my invention to provide an economical and simple method and devices for tone shaping the sinusoidal oscillators of an electronic musical instrument.

It is a further object of my invention to provide simple non-linear tone shaping circuits for use in modifying the output of individual sinusoidal oscillators of an electronic musical instrument. 7

Other objects and advantages of my invention will be apparent during the course of the following description.

In the accompanying drawings, forming a part of this application, and in which like numerals are employed to designate like parts throughout the same,

Figure 1 is a block diagram of a portion of an electronic organ of the type mentioned above,

Figure 2 is a simplified block diagram which is utilized to illustrate and explain the underlying principle of my invention,

Figure 3 is a plot of capacitance and capacitive reactance against voltage for non-linear capacitors and serves to further illustrate the underlying operation of my invention,

Figure 4 is a schematic diagram of several embodiments of my invention, and

Figure 5 is a schematic of several further embodiments of my invention.

In the drawings, wherein for the purpose of illustration, I are shown preferred embodiments of my invention, the

numeral designates an electronic organ console, generally, a small portion of which I have chosen to illustrate my invention. It should be clearly understood that my invention may be applied to all of the organ or to any part of it to which it is desirable to add tone shaping. It is also to be understood that the methods and devices of my invention, which are described for use with an electronic organ, are equally applicable to other electronic musical instruments such as electric pianos, accordions, and like instruments.

The position of the keyboard chosen to illustrate my invention comprises the key F, numeral 11, and the five half-tones immediately above 11 in frequency through to key A, numeral 24. The other keys are designated as follows: 15; G, 22; and G#, 23, All keys operate atent in the same general manner so that it is suificient to describe the operation of key 15 and its associated circuitry to adequately explain the principles and technique employed in my invention. When key 15 is depressed, power is connected to oscillator 13 by the closing of the contact 17 which connects bus 16 and bus 3.7a. The output of oscillator 18 is fed to the input of each of the tone shaping elements 19, 2t and 21 whose characteristics may be fixed or variable depending upon the particular design of the electronic musical instrument in which they are installed. The output of tone shaping element 19 is fed to bus I, the output of tone shaping element 20 is fed to bus ii and the output of tone shaping element 21 is fed to bus III.

The output of bus I is fed to preliminary amplifier 37 through switch 34, the output of bus 11 is fed to preliminary amplifier 38 through switch 35, and the output of bus III is fed to preliminary amplifier 39 through switch 36. The outputs of the preliminary amplifiers 3'7, 38 and 39 are fed to amplifier 40 whose output is connected to loudspeaker 4-1. Switches 34, 35' and 36 are commonly referred to as stops and serve for example to make all keys string, flute, diapason, or any of the other usual organ stop effects or combination of effects depending on the tone shaping provided by the particular tone shaping elements.

My invention relates to economical and easily produced tone shaping elements which may be employed in conjunction with each individual key of an electronic organ manual, or other electronic musical instrument. Oscillator 25 which is actuated by key 2?. feeds tone shaping elements 28, 29 and in the same manner as has been previously described. In like manner, oscillator 26 feeds tone shaping elements 31, 32 and 33. Oscillators 14 and 27 also feed similar tone shaping elements which are not shown in the drawing. Key 11 actuates oscillator 14 by connecting bus 12 to bus 13a through contact 13. All other keys actuate their associated oscillators in a similar manner. However, other methods for actuating the individual tone oscillators may also be employed. Tone shaping elements 28 and 31 are connected to bus I, tone shaping elements 29 and 32 are connected to bus II and tone shaping elements 39 and 33 are connected to bus III.

Figures 2 and 3 serve to illustrate the operation of the tone shaping elements produced in accordance with my invention. The numeral 42 designates a source of alternating voltage and may represent any of the sinusoidal oscillators of an electronic musical instrument. The output voltage of 42 is designated as E and the voltage across 44, impedance Z is designated as E Impedance Z which is in series with 42 and 44 is designated by the numeral 43. Either 44 or 43, or both of them, may be non-linear impedances.

In Figure 2,

so that it both Z and Z vary in accordance with the value of the input voltage E E will not bear a linear relationship to E. This will also hold true if either Z or Z is non-linear and varies in accordance with the value of the input voltage E Assume that Z is a nonlinear capacitor whose capacity varies in accordance with the applied voltage as illustrated by curve C of Figure 3. Then its capacitive reactance varies in accordance with the applied voltage as illustrated by curve X of Figure 3. If the impedance of Z, is substantially higher than that of Z E will be approximately proportional to E Z And since Z is equal to X in this case, then E is approximately equal to E X if a sinusoidal voltage is applied as E, in addition to a biasing directcurrent voltage E curve 45, so that operation of the circuit is at point I on curve X the resulting curve, which represents E will be of the form of curve 46. In a similar manner, curve 47 represents operation at point K of the curve. Frequency doubling and half-wave rectification occurs when operation takes place at point L of the curve. Curve 4% illustrates the resultant wave shape for such operation. This operation at point L is possible because the ferroelectrics such as barium titanate are not polarity sensitive.

A similar analysis may be carried out for non-iinear element 43, in which case, a maximum change in the Wave shape'or" E with respect to that of E will occur when the impedance of 44 is considerably lower than that of 43.

Coils wound on cores made of any of the ferromagnetic ceramics exhibit an eifect similar to that described above except that the inductive reactance rather than the capacitive reactance varies with the applied current. Similar analysis to that given will hold equally well in such cases in which either 43 or 44 is a non-linear inductance. More complex Wave shapes are obtained when both and 44 are impedances which are functions of applied voltage and current and when either or both of them are combinations of linear and non-linear capacitors and inductors, used with or without other linear or non-linear circuit elements. Non-linear transformers, Whose mutual inductance is dependent on the applied current, may also be employed as the non-linear circuit elements.

Figure 4- illustrates several non-linear tone shaping circuits at the output of oscillator 57 and feeding various output buses. Non-linear capacitor 59 feeds bus IV and is operated as an unbiased element in the position of 43 of Figure 2. Bus V is fed by non-linear capacitor 54 in the position of 43 of Figure 2 with the addition of D.-C. bias supplied by battery 55. Bus VI is fed by unbiased non-linear inductor 49 in the position of 43 of Figure 2. Bus VII is fed by non-linear inductor 51 in the position of 43 of Figure 2. The operating point is biased by the application of a D.-C. bias from the battery 53 through secondary winding 52. Bias of nonlinear inductors may also be accomplished by applying a permanent magnetic field to the inductor. Non-linear capacitor 56 feeds bus VIII and is in the position of 44 in Figure 2. It is operated without bias. Other arrangements and configurations may be utilized to produce the various effects desired.

Figure 5 illustrates still further embodiments of my invention. Bus IX is fed from a small trandormcrfifi which is biased by the vacuum cathode current and whose mutual inductance is non-linear. A miniature toroidal core of ferromagnetic ceramic material may be employed to produce transformers with non-linear mutual inductance. Non-linear transformer 59 supplies bus X and is unbiased. The inductance of 58 and 59 is small with respect to main tuning inductance 60 so that the fundamental frequency of the oscillator 61 is not materially afiected. Bus XI is fed from the junction of capacitors 62 and 63 either or both of which may be linear or nonlinear depending on the type of effect desired.

While I have described my invention by means of specific examples and in specific embodiments, I do not Wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit of my invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. An electronic musical instrument comprising in combination a plurality of oscillators,,each characterized by a substantially sinusoidal output current, individual shaping circuits respectively interposed in the output paths of said oscillators, each of said shaping circuits including at least one reactance element comprising a material selected from the group consisting, of ferroelectric and ferromagnetic materials.

2. An electronic musical instrument as described in claim 1 wherein at least one of said reactance elements is capacitive.

3. An electronic musical instrument as described in claim 1 wherein at least one of said reactance elements is inductive.

4. An electronic musical instrument as described in claim 1 wherein at least one of said reactance elements is capacitive and at least one is inductive.

References Cited in the file of this patent UNITED STATES PATENTS 2,142,580 Williams Jan. 3, 1939 2,182,377 Guanella Dec. 5, 1939 2,289,564 Wrathall July 14, 1942 2,403,664 Langer July 9, 1946 2,462,423 Polydorff Feb. 22, 1949 2,649,006 Heytow et al Aug. 18, 1953 

